David Jimenez

A set is an unordered collection containing no duplicates. Common operations on sets include intersection, difference, and union.  C# provides at least two ways of performing these operations: one is using LINQ extensions; the other, is Hashset, a generic collection.

Sets in C#

This is the first in a series of posts to model a traffic light. The goal is to showcase TLA+ usefulness in modeling software, and along the way, introduce concepts key to the language. One of those key concepts is that of <code>state</code>
In TLA+, a system's <code>state</code> is defined by the assignment of values to variables. A traffic light has three signals: red, yellow, and green. We can say that these are the traffic lights' variables. The values these variables can take are either on or off. We can represent <code>on</code> with a one, and <code>off</code> with a zero.
Thus a traffic light can have three valid states:
<ul>
<li><code>red</code> = 1, <code>yellow</code> = 0, and <code>green</code> = 0 (this is when we say the light is red).</li>
<li><code>red</code> = 0, <code>yellow</code> = 1, and <code>green</code> = 0 (this is when we say the light is yellow).</li>
<li><code>red</code> = 0, <code>yellow</code> = 0, and <code>green</code> = 1 (this is when we say the light is green).</li>
</ul>
A traffic light transitions between these three states. These transitions between states are called <code>steps</code>.

When modeling a system we have to determine how we are going to represent its state.  In this post we explore how to do that for a traffic light.

Modeling a traffic light - Part 1: State

This post explores what TLA+ is and why it may be worth using.